Means for determining screen size for well screens



April 14, 1953 M. J. NAPIER 2,634,613

MEANS FOR DETERMINING SCREEN SIZE FOR WELL SCREENS Filed Aug. 2, 1950 2 SHEETSSHEET 1 FIG. I

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J uzwm ug pnza ATTORNEYS M. J. NAPIER A ril 14, 1953 MEANS FOR DETERMINING SCREEN SIZE FOR WELL SCREENS 2 SHEETS-SHEET 2 Filed Aug. 2, 1950 ATTORNEYS Patented Apr. 14, 1953 cgmsrgon DETERMINING senses s ze.

' EQH' QE ENQ Melvin J Napier, Akron, Ohio, assignorto Boiler'l & Machine Company, I nc.,' Akron,

a. c012i)oration.of:v Ohio M ami. QhiQ ePvl eiiee efi si .'.$erie 3 4--Glaims. (Cl. 7 3.-.432;)

h mv niioa elate w l. d i n a n ar icul Q- ans 9? hi e e ini h id z bb n cre n be n er e he. i e unk atmrb ri s an s In the "drilling of wens; a pipe, is driven by degrees into the ground; whichis prepared by eta wo king in advance a; the pipe. "From time to tiri'l' samples or thefwater inthe. pipe, Wit -fs ne id'e mat arev B ou t e. r- 'e sb gm ea n xami d m a? h at re; i. he. ra a in. whi h o tom otthe pipe is' located, until asand strata is indicated. 'The underground structure is then completed by dropping 'a tubular well screen through the pipe intothe sand strata raising the pipe to the top of the screento uncover it, and

securing the bottom a: the pipeto the top of the screen tube. Thereafter, the sand surrounding the screen is conditioned by what'isknown as surging,'whereinthe waterof the sand is worked back and forth through the screen, from thesand n t e u ni' ee mit Qfxih ube nto h sand; In this operationthe finer s'and'is worked away until a zone of: onlythe coarser'sand particles" is built uparoundthe screen. This conditioh persists thereafter and'water which is free of -flne 'san'dmay thereafter be'drawn into the wnfpipe.

In' order to achieve maximumrateof volume delivery of Water, the screen size must be adapted to the particle size Characteristics df the sand andit has become accepted asa ruleof thumb thato'ptirnum' delivery may be expected if the fraction of "sand retained by the screen represents 40.% ofthe totalsand,

Heretofore, in the selection of proper screen size,'the drillershaveeither estimated the particle size analysis by inspection'of a sample at the well site orhave actually performed analyses with screen's. In the lattr method,- the sand has to be "dried and then shaken-through a screen. The first-method o'f'estimationis liable to large errors which may entail subsequent replacement of a screen placed in the weli pipe. The second is time consuming and doesnot r'eproduce' actii'al' conditions in the well under SurgingI The problem is" sd'cr-itioal that drillers have frequently sent. samples" to remote: laboratories for" screen anaiysis. This latter" method} 'while repre n mg by far the" largesttime 1delavof the three, is also. unreliable as" failing "tereflect' actual c'onditions inthesurg'ing operation 'and the recoxii-rnendations t o"screen si'ze h'av been known to .be. so far} in rror'as replaeementSoLthe sci'eeiiQ are eibs ede et.

Bythe present invention, 1 haveprovi-ded for accurately determining. properscreensize in. a minimum of time at the site of: the. well by reproducing the actual conditions' of surging-in a test apparatus.

It is, therefore, an object of the invention to provide for determination of reliable test data relative to screen sizes forwells. A further object is to provide fortest data as to screensize for sands in wells, in a minimum oftime, at the well site, by simple and inexpensive equipment which does not require special skill in the handling. In particular it is an object to provide means for screen size determination by repro: ducing conditions of actual well operation. More specifically, it is an object to determine proper well screen size by surging water back and forth through a test screen similar to an actual well screen.

These and other objects will be apparent to those skilled in the art from the accompanying description of the invention as illustrated in the drawings, in which:

Fig; 1 is a side elevation inpartial axial section of a test screen, in place in a sand-holcb g p i s Fig. 2 is a top plan view of the parts shown in-Fig'. 1-,

Fig. 3 is an elevational view ofa test apparatus'beingimmersed in water,

Fig. 4 is a view similar to Fig 3, showing the test apparatus beinglifted out of the-water, after a plurality of immersions,

Fig. 5 is a sectional view taken on the line 5-5 ofFig. 3, and

Fig. 6- isa sectional view taken on the line 66of Fig. 4.

Referring tothedrawings by charactersof reference, there is shown inFigs. 1 and.,2, a test screen ll! of cylindrical form; which is a foreshortened length of screen ofthetype permanently installed in well pipes. The particular screen chosen for illustration is composed of cop: per tubing of 1% inch; wall thickness, 3 /2, inches outsidediameter, and} inches-in length.

"The screen opening .are provided in acircum ferentially arranged series of louvers. comprising strips II outwardly struck iro'mi'the cylinderfl fl. Strips II are about inches wide, arespaced apart a distanceabout equal'to their width and the openings are about inch inheight The outward radial distance of louvers ll from the surface of tube 10 determinedthesize of screen ope g an medial wa l screensthisw 11 ary with the grain'size of the sands in which the screen is to be used, the range of sizes of openings being from about 0.003 inch to 0.050 inch. It will be understood that the screen pattern is conventional and forms no part of the present invention. In the actual well screens, the circumferential series of louvers are provided in plurality along the tube, but in the test screen only one such ring of louvers is necessary, and in fact it is preferable to use one only.

The louvers are spaced from the bottom, to provide a lower margin I2, adapted for insertion in snug relation in the depending neck I3- of a cup I 4. The latter i cylindrical and concentric with and spaced from screen tube I 0. Cup I4 and neck l3 are joined by an annular shelf I 6,- against .which louvers II abut to limit movement of screen I through neck I3.

The space I? between tube I0 and cup I l forms an annular chamber to hold the sand sample and if lower margin I2 of tube I0 is snugly fitted in neck I 3 of the cup, the only communication from chamber I! to the inside of the tube is through the openings at the louvers.

The cup shown has a wall thickness of about ,5, inch, the diameter of the larger, upper portion is about five inches, which provides a width of about inch in the chamber ll, and the inner diameter of neck 13 is just enough larger than the outer diameter of tube It to provide a sliding fit, without passing fine sand. Tube i0 preferably extends slightly above cup 14, so that the tube may be conveniently grasped by the fingers at the extremities of a diameter when inserting it into or removing it from the cup. The bottom of tube Iii preferably terminates short of the bottom of cup neck I3, so that the position of'the screen openings relative to the cup will not be accidentally displaced.

If the chamber I? be filled with a sample of sand from the well, conditions of actual use of the screen may be simulated. Thus, assuming that in the drilling, of a well a likely looking sand strata has been reached, a sampling is made in conventional manner and is placed in the chamber I! of the test apparatus, in any predetermined, standard amount, up to a reference line, or to the top of cup E4. The sand is in fully dispersed condition, respecting size distribution, as it existed in the sand strata.

The next step is to separate the fine sand from the aggregate by surging, in simulation of the actual process by which the fine sand is eliminated and the coarser particles piled up about the screen openings in the well itself. This step in the test method is illustrated in Figs. 3' and a. In Fig. 3, the test unit is shown as being immersed in a body of water I8 contained in any convenient vessel I9, such as anordinary bucket. As shown by'the arrows, the water passes within tube III and through the louver openings lnto the sand-filled chamber II. The sand is indicated by the numeral 2| and Fig. 3 illustrates the first immersion of the unit with the sand particles still randomly dispersed. As the water passes into the sand, it carries the fine particles away from the openings and agitates the coarser particles so that they rearrange themselves in a manner which becomes more or less permanent in pattern with each successive immersion cycle or surging operation. Following immersion, the test unit is iifted. from the water, as illustrated in Fig. 4, whereupon the water in the sand 2i drains on through the screen openings, carrying with it the finer sands, which pass through the interstices among the coarser sand particles.

After a number of cycles of immersion and withdrawal, the sand content in chamber I! will have reached a condition wherein all of the fine particles which are capable of passing through the array of coarse particles piled up at the screenopenings, have passed out of the test unit. This is the condition shown in Fig. 4. The percentage of sand remaining in the chamber can easily andreadily be determined by inspection, from its height in the chamber, and drying and weighing are therefore unnecessary.

In the use of the apparatus, the test screens I 0 will be providedin a series with different sizes of openings. For any given sample, a test screen may be selected after rough estimation of the character of' the sand, and a test run made. If

more than 60% of the sand is lost, a smaller screen opening is tried, and if less than 60% of the sand is lost, a larger screen opening is tried, and so on, until the proper screen size is determined. Of course, the 40%-60% standard is arbitrary, but the method is qualified to give accurate data, regardless of the standard em ployed. On the average, determination of. Droper screen size, according to this invention, may be made in from one tothree minutes. a

Although the rings of louvers occur inplurality in the actual well screens, it is preferable to use only one in the test cylinder, since any louvers at higher levels would be utilized only during a. part of the filling and draining processes and the results would be less likely to reflect actual conditions. V

The present invention is to be distinguished from conventional fractionation practicein the analysis of aggregates. ,In such cases, fr actions are completely separated, insofar as possible. In the use of well screenswhere the force tending to move the particles through a screen is a moving stream of water, the retained particles are not necessarily larger than the screen openings, since particles smaller than such openings may, and in fact do, jam up in such a way as to interlock and resist passage of particles which would otherwise pass through the screen. Thus, in using a test method which simulates the surging through well screens, the invention not only gives valuable test data but employs a screening test device which is novel in the art of testing.

Although outwardly struck, vertical louvers have been shown, other types of screen are employed in wells, which are'also conditioned by surging. Therefore, the method and apparatus shown and described herein are not limited to the type of screen shown. Also, the-screen and cup may be integral, but it is preferable to have a single cup for a seriesof test screens. In general, changes may be made in the size, shape, and arrangement, for instance, of the various parts of the present invention, without departing from the spirit or-scope of the appended claims.

What is claimed is:

a 1. A portable test unit for determining suitable well screen size for a given well, comprising a right, circular, cylindrical element having outwardly struck portions defining openings through the wall of said element, and a right, circular, cylindrical imperforate receiving member for said element having a portion spaced outwardly of said element to define an annular chamber, and a portion receiving a free end of said element in a close,,sl idin fitrsaid struck portions being arranged circumferentially about said element and extending into said chamber so as to limit the extent of movement of said element into said second-mentioned portion.

2. For use with a section of cylindrical well screen, for determining suitability of the screen size for a given well, a portable, right, circular, cylindrical receiving member for holding a quantity of sand in surrounding relation to said screen, said member being entirely imperforate and comprising a first, cylindrical portion, a second, cylindrical portion concentric with and of smaller diameter than said first portion, and an annular wall connecting said portions, said portions being disposed on opposite sides of said annular wall, and said portion of smaller diameter adapted to receive a section of well screen in a close, sliding fit.

3. A portable test unit for determining suitable well screen size for a given well, comprising a right, circular, cylindrical element having wall openings to provide a screen, a right, circular, cylindrical imperforate receiving member for said element, having a portion spaced outwardly of said element to define an annular chamber, and a portion receiving a free end of said element in a close, sliding fit, and means limiting extent of movement of said element into said receiving portion.

4. A portable test unit for determining suitable well screen size for a given well, comprising a right, circular, cylindrical element having wall openings to provide a screen, a right, circular, cylindrical imperforate receiving member for said element, having a portion spaced outwardly of said element to define an annular chamber, and a portion receiving a free end of said element in a close, sliding fit, and means limiting extent of movement of said element into said receiving portion, with said free end of said member lying within said receiving portion.

MELVIN J. NAPIER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 910,696 Layne Jan. 26, 1909 1,274,121 White July 30, 1918 1,756,597 Keenan Apr. 29, 1930 OTHER REFERENCES Testing Sieves, Catalogue 53, 1940 edition 209/237, Tyler 00., Cleveland, Ohio. 

